They both mean the same thing: easily set on fire.
It might seem confusing since "in" often means the opposite of something, but in this case, "inflammable" simply comes from the Latin "inflammare" meaning "to set on fire."
They both mean the same thing: easily set on fire.
It might seem confusing since "in" often means the opposite of something, but in this case, "inflammable" simply comes from the Latin "inflammare" meaning "to set on fire."